Double-index averaging: A novel technique for dynamic element matching in Sigma-Delta A/D converters

We report the study of a second-order Sigma-Delta modulator for audio appli cations with a nine-levels quantizer, The feedback digital-to-analog has be en implemented with four capacitors and two voltage references, taking the structure typical of fully differential systems. We first discuss the perfo rmance achievable with the most popular dynamic element-matching techniques , namely the data-weighted averaging and individual-level averaging. We the n introduce a new algorithm, the double-index averaging, that performs bett er than the other algorithms by 10-15 dB over the entire dynamic range of t he modulator, and 6 dB at the peak of signal/(quantization noise + total ha rmonic distortion).